Vehicle brake part



3,318,423 Patented May 9, 1967 3,318,423 VEHICLE BRAKE PART WalterDunki, Zurich, Switzerland, assignor to Escher Wyss Aktiengesellschaft,Zurich, Switzerland, a corporation of Switzerland No Drawing. FiledSept. 8, 1964, Ser. No. 396,275 Claims priority, applicationSwitzerland, Oct. 10, 1963, 12,453/ 63 11 Claims. (Cl. 188-251) PercentCarbon 3 to 3.3 Graphite 2 to 2.5 Silicon 1.8 Phosphorus 60.8 Sulphur0.15 Manganese 0.45

With vehicle brake parts subjected to stress by sliding friction it isintended to obtain a good braking effect, and also the wheels or wheelrims should be protected as much as possible. In vehicle brake partssubjected to stress, considerable wear is an undesirable occurrence. Thewear dust consists partly of reddish-brown rust, which can be verytroublesome. As the result of Wear, the brake parts have always to bereplaced after a comparatively short service period. Attempts havealready been made, inter alia by varying the alloy composition, toeffect a reduction in wear. Thus, for example, the phosphorus contenthas been increased, in some cases up to 1.5%, or small additions ofchromium up to 1.5%, and of molybdenum or vanadium up to a few tenths ofa percent, have been made. Wear has thus been reduced somewhat, but thebraking effect was impaired, and to some extent, the braking surface ofthe wheel or tyre has been damaged. Heretofore, it has not been possibleto employ successfully brake shoes of such cast iron, or they have notbeen accepted in practice.

This invention now consists in that a vehicle brake part subjected tostress by sliding friction is made of a highcarbon, austenitic ironalloy having a proportion of free carbon.

It has been surprisingly found that brake parts of the aforesaidmaterial have excellent service properties. This was not to be expected,since such a material costs several times more than, for example, thematerial used heretofore for brake shoes, and it is only possiblebecause unexpected braking properties are obtained by means of suchaustenitic material, namely very low wear coupled with the best brakingeffect and maximum protection, for example, also of wheels and tyres. Bythis means, the resulting life is increased by several times, so thatdespite the high cost, the result is a considerable economic advantage.Austenitic structure of the material is preferably obtained by a nickeladdition of between and '25 Some of the nickel may also be replaced bymanganese in an amount of between 0.5% and 7%.

In addition to the two austenite formers-nickel and manganeseit has beenfound advantageous to add also a certain copper content, which dissolvesin the austenite, and may amount to from about 0.5 to 4%. It isfurthermore advantageous to imbed in the groundmass, in addition toaustenite, hard constituents, such as carbides, phosphides and so forth.The following come into consideration for this purpose: iron carbide andcarbides of carbideforming elements such as chromium, molybdenum,vanadium, and titanium, as well as phosphorus. The addition of chromiummay amount to about 0.5 to 3%, that of molybdenum, vanadium and titaniumeach to about 0.1 to 1% and that of phosphorus to about 0.6 to 1.5%.

Part of the carbon is present in the alloy in the free form as lamellaror spheroidal graphite. The latter form of graphite is obtained bytreatment with the addition of magnesium or cerium or both. Such anaustenitic cast iron for brake parts has, for example, the followingtypical analysis:

Percent Carbon 2.8 Silicon 2.3 Phosphorus 0.6 Sulphur 0.06 Nickel 19Manganese 1.5 Copper 2.0 Chromium 0.1

Ordinary Austenitic cast iron cast iron Tensile strength, kg/n'nn. 15 to20 35 Elongation, percent 1 10 to 40 Notch impact toughness, kgm./cm. 0.3 3 Brinell hardness, kgJmrn. 180 to 250 to 60 It must also be pointedout that austenitic cast iron for brake parts practically does not rustor is almost rustless.

The invention may be used not only for brake shoes, acting on the wheelrims of railway vehicles, but also for other brake parts, which aresubjected to stress by sliding friction, for example for brake discs.

What is claimed is:

1. A vehicle frictional brake part subjected to stress by slidingfriction, consisting of a high-carbon, austenitic iron alloy having aproportion of free carbon.

2. A brake part according to claim 1, in which the austenitic structurecomprises a nickel addition of 10% to 25%.

3. A brake part according to claim 2, in which for austenite formation,part of the nickel has been replaced by manganese from 0.5% to 7%.

4. A brake part according to claim 1, in which the material contains 0.5to 4% copper.

5. A brake part according to claim 1, in which the material contains 0.5to 3% chromium.

6. A brake part according to claim 1, in which the material alsocontains addition of 0.1 to 1% of at least one of the materialsmolybdenum, vanadium and titanium.

7. A brake part according to claim 1, in which the material contains 0.6to 1.5% phosphorus.

8. A brake part according to claim 1, in which the carbon content ispresent partly in carbide form and partly as free carbon (lamellaegraphite).

9. A brake part'according to claim 1, in which the free carbon ispresentin spheroidal form.

10. A brake part according to claim 1, in which the material issubjected to a heat treatment by annealing between 800 C. and 1000 C.

11. A vehicle frictional brake part subjected to stress by slidingfriction consisting of a high-carbon austenitic iron alloy having aproportion of free carbon, comprising the components nickel, carbon,silicon, copper, manganese, phosphorus, chromium, sulphur substantiallyin the proportions" 19%, 2.8%, 2.3%, 24.0%, 1.5%, 0.6%,

0.1%, 0.06%, respectively.

References Cited by the Examiner UNITED STATES PATENTS 7/1958 Guenzi75---125 9/1962 Schelleng et al. 75-123 FOREIGN PATENTS 807,302 10/1936France.

1. A VEHICLE FRICTIONAL BRAKE PART SUBJECTED TO STRESS BY SLIDINGFRICTION, CONSISTING OF A HIGH-CARBON, AUSTENITIC IRON ALLOY HAVING APROPORTION OF FREE CARBON.